Maximum Pulse Research Articles

Single frequency pulsed Er,Yb co-doped fiber amplifier with 2 mJ of output energy

High-energy single-frequency pulsed light with low noise is generated from a master oscillator power amplifier (MOPA) system at 1.55 μm eye-safe wavelength using an ultra large mode area Er-Yb gain fiber. At a pulse repetition rate of 2 kHz, the maximum pulse energy without stimulated Brillouin scattering (SBS) reaches 2.07 mJ with 375 ns pulse duration for a pump power of 56.4 W. The pulse energy fluctuation is approximately 0.72 % within 21.5 min. The signal noise ratio (SNR) from the single-frequency fiber amplifier, at the highest pulse energy, centered at 1551.1 nm, is approximately 30 dB. The spectral half width of the signal light is calculated to be 1.28 MHz, which is close to the transform limit.

Q-switched EDFL with copper phthalocyanines saturable absorber

We have successfully demonstrated Q-switching within the confines of an erbium-doped fiber laser (EDFL) cavity. This innovative approach leveraged copper phthalocyanines (CuPc) as a saturable absorber (SA), with the SA film made via the embedding method utilizing polyvinyl alcohol (PVA). The Q-switched EDFL achieved a minimum pulse width of 3.95 µs, a maximum pulse rate of 77.2 kHz and a maximum pulse energy of 49.2 nJ as it operated under a maximum pump power of 102.8 mW. Notably, this pioneering work marks the first instance of employing a CuPc PVA-based SA to produce a Q-switched laser within the 1.55 µm region. Our findings offer exciting prospects for advancements in Q-switched fiber laser technology.

Research on morphology, porosity, mechanical properties of 7075 aluminum alloy repaired by arc welding and laser shock forging

There are many problems in the arc welding repair of aluminum alloy parts, such as excessive pores, coarse grains, and low hardness. Introducing external energy excitation is an effective solution. In this paper, 7075 aluminum alloy parts are repaired using the arc welding - laser shock forging technique. The effects of laser-wire spacing, laser pulse energy and frequency, welding current and speed, and V-groove depth on the surface morphology, section geometric characteristics, and porosity of the repaired layer are studied. Additionally, the hardness and microstructure of the repaired layer formed by arc welding - laser shock forging and arc welding are compared. The results show that a fine surface morphology of the repaired layer can be achieved by selecting reasonable laser-wire spacing, welding current, welding speed, and V-groove depth. It is also advised to select the maximum laser pulse energy and frequency possible, in order to increase the aspect ratio, reduce the residual coefficient, minimize porosity, and decrease the maximum pore diameter of the repaired layer. When compared to arc welding alone, arc welding - laser shock forging has the advantage of reducing grain size and improving the hardness of the repaired layer.

Generation of mode-locked thulium doped fluoride fiber laser using graphene-zinc oxide (G-ZnO) coated dual arc-shaped fiber

In this work, mode-locked laser generation at the S-band region was achieved using a graphene-zinc oxide (G-ZnO) coated dual arc-shaped fiber as a saturable absorber (SA) within a thulium-doped fluoride fiber (TDFF) ring cavity. Two-step polishing was implemented to fabricate a dual arc-shaped fiber, and a G-ZnO solution was then deposited on the dual arc region via the drop-casting method to form the SA. Mode-locked pulses were generated by incorporating the G-ZnO-based SA into the TDFF ring cavity, with the pulses having a central wavelength, 3 dB bandwidth and pulse duration of 1503.4 nm, 0.68 nm and 3.52 ps, respectively. At the maximum pump power of 202 mW, an average output power of 2.47 mW was obtained with a maximum pulse energy of 6.16 nJ and a peak power of 1.75 kW. At this pump power, the generated pulses have a frequency of 401.6 kHz with a signal-to-noise ratio (SNR) of 54 dB. The mode-locking threshold was at a pump power of 118 mW. The results obtained in this work indicate the potential of a new class of 2D composite materials which can be used as nonlinear optical devices.

Molybdenum gallium carbide saturable absorber as Q-switcher in an erbium-doped fibre laser

In this research work, molybdenum gallium carbide (Mo2Ga2C)—fabricated as a thin film via solution casting technique—was first introduced as a saturable absorber (SA) to regulate the intracavity losses in a Q-switched fibre laser. The fabricated Mo2Ga2C SA had undergone both optical and physical interpretations prior to its employment as a Q-switcher in an erbium-doped fibre laser (EDFL) ring cavity configuration, sandwiched in between the end-facets of the optical fibre ferrules. The Q-switched wavelength was observed at 1532.07 nm and the Q-switching parameters were determined, accordingly. The temporal parameters of Q-switched EDFL, which include the maximum pulse repetition rate, minimum repetition period and minimum pulse duration were indicated as 107.60 kHz, 9.29 μs, and 5.52 μs, correspondingly. The maximum output power, peak power and pulse energy of the Mo2Ga2C-PVA SA as the Q-switcher were 7.3 mW, 11.47 mW and 67.38 nJ, in accordance with a slope efficiency of 7.39 % and signal-to-noise (SNR) ratio of 57.6 dB.

Energy-scaling of a diode-pumped Alexandrite laser and prototype development for a compact general-purpose Doppler lidar.

We present design and performance data of an energy-scaled diode-pumped Alexandrite laser in single longitudinal mode operation developed as a beam source in a mobile general-purpose Doppler lidar. A maximum pulse energy in Q-switched operation of 4.6mJ and a maximum average power of 2.7W were achieved for a repetition rate range from 500 to 750Hz with excellent beam quality of M 2=1.1. Two rugged and compact demonstrator lasers were built and integrated into mobile lidar systems, where a bandwidth of approximately 3MHz is measured. Measurements of atmospheric winds and temperatures were conducted during several field campaigns from summer 2022 to spring 2023.

Dual-loss-modulated QML erbium-doped fiber laser with microfiber and NPR technique

We demonstrated a dual-loss-modulated Q-switched mode-locked (QML) erbium-doped fiber laser based on the nonlinear polarization rotation (NPR) technique with a microfiber. The microfiber served as both a highly nonlinear medium and a saturable absorber, which together with the NPR technique enables stable QML operation under significant pump power fluctuations. We evaluated the nonlinear properties of microfibers with different waist diameters. A maximum QML envelope energy of 467.15 nJ is achieved, corresponding to an average single-pulse energy of 4.06 nJ beneath the Q-switched envelope, which is 2.35 times higher than the maximum pulse energy attained with dissipative soliton mode-locking under similar pump power. In addition, the QML laser was verified by numerical simulation based on the coupled Ginzburg-Landau equation. The microfiber's customizable size enables significant variations in non-linear and saturable absorption characteristics, creating the potential for QML pulse regulation. This research provides novel insights for designing QML lasers.

Ti3C2Tx saturable absorber (SA) as Q-switched initiator in passive neodymium doped fiber laser (NDFL)

Q-switched fiber lasers have sparked the curiosity of researchers due to their numerous applications in fields including communication technology, material processing, remote sensing, and medicine. Drop casting was used to create the MXene Ti3AlC2 by dropping the solution onto the fiber ferule and allowing it to dry at room temperature. The MXene Ti3C2Tx was made using a selective etching technique on MAX Ti3AlC2. The modulation depth of MXene Ti3C2Tx liquid-based SAs is 5.6 %. The Q-switched has a input power range of 105 mW to 152 mW, a repetition rate of 26.6 kHz to 33.8 kHz, and a maximum pulse energy of 8.68 nJ. The maximum average output power and peak power are 0.30 mW and 2.76 mW, respectively.

Monolithic tapered Yb-doped fiber chirped pulse amplifier delivering 126 μJ and 207 MW femtosecond laser with near diffraction-limited beam quality

In this work, a high-energy and high peak power chirped pulse amplification system with near diffraction-limited beam quality based on tapered confined-doped fiber (TCF) is experimentally demonstrated. The TCF has a core numerical aperture of 0.07 with core/cladding diameter of 35/250 µm at the thin end and 56/400 μm at the thick end. With a backward-pumping configuration, a maximum single pulse energy of 177.9 μJ at a repetition rate of 504 kHz is realized, corresponding to an average power of 89.7 W. Through partially compensating for the accumulated nonlinear phase during the amplification process via adjusting the high order dispersion of the stretching chirped fiber Bragg grating, the duration of the amplified pulse is compressed to 401 fs with a pulse energy of 126.3 μJ and a peak power of 207 MW, which to the best of our knowledge represents the highest peak power ever reported from a monolithic ultrafast fiber laser. At the highest energy, the polarization extinction ratio and the M2 factor were respectively measured to be ~ 19 dB and 1.20. In addition, the corresponding intensity noise properties as well as the short- and long-term stability were also examined, verifying a stable operation of the system. It is believed that the demonstrated laser source could find important applications in, for example, advanced manufacturing and photomedicine.Graphical

Q-switched pulse generation by stimulated Brillouin scattering assisted four-wave mixing effect in erbium–bismuth co-doped multi-elements silica glass based optical fiber laser

We demonstrate Q-switched pulse generation at the 1562.5 nm region by using a 70 cm long erbium–bismuth co-doped alumina–germania–hafnium–yttria silica glass-based fiber as a gain medium in a simple ring resonator configured without saturable absorber and optical isolator devices. The Q-switching was obtained based on a stimulated Brillouin scattering assisted four-wave mixing effect in the gain medium, which induced the intensity modulation mechanism. The laser produced a multi-wavelength output comb centered at 1562.6 nm with a peak-to-peak spacing of about 0.09 nm due to nonlinear effects. Stable Q-switched operation of a hafnia–bismuth–erbium co-doped fiber laser was obtained at a pump power range of 129–319 mW with the repetition rate varying from 45.9 kHz to 89.3 kHz and the pulse width ranging from 8.8 µs to 3.58 µs. A maximum pulse energy of 26.9 nJ at an average output power of 2.4 dBm was achieved. This demonstrates a new passive technique based on a highly nonlinear gain medium for realizing Q-switched all-fiber laser sources.

Generation of Q-switched erbium-doped fiber laser using MAX phase titanium aluminum nitride Ti4AlN3

We achieved a self-induced Q-switched erbium-doped fiber laser (EDFL) operating at 1559.4 nm through the integration of a Titanium Aluminum Nitride, Ti4AlN3 MAX phase film as a saturable absorber (SA). The MAX phase was embedded into a polyvinyl alcohol (PVA) matrix, ensuring contamination-free compatibility. The SA film demonstrated a modulation depth of 17% and saturation intensity of 0.5 MW/cm². Integration of the film enabled stable Q-switching, producing pulses with 5.75 µs width at 59.2 kHz repetition rate and 29.9 – 64.7 mW pump power. Parameters included a maximum average output power of 2.34 mW, maximum pulse energy of 39.5 nJ, and highest peak power of 6.87 mW. The RF spectrum exhibited a 63 dB signal-to-noise ratio, indicating high pulse signal quality. This demonstration of Ti4AlN3 MAX phase film Q-switched fiber laser holds promise for applications including biomedicine.

Self-induced Q-switched fiber laser using tantalum aluminum carbide as a passive modulator

A self-induced Q-switched erbium-doped fiber laser operating at 1563 nm was achieved by integrating a passive modulator based on tantalum aluminum carbide (Ta2AlC) MAX phase film embedded into polyynyl alcohol. The modulator, serving as a saturable absorber (SA), established a modulation depth of 9% and a saturation intensity of 0.3 MW cm−2. Upon integration of the film SA, a stable Q-switched fiber laser was obtained, generating pulses with a minimum width of 7.6 µs at a repetition rate of 45.1 kHz, within a pump power range of 24.9–59.7 mW. The corresponding maximum average output power, maximum pulse energy, and highest peak power were determined at 1.6 mW, 36.2 nJ, and 4.7 mW, respectively. The RF fundamental spectrum exhibited a good signal-to-noise ratio of 61 dB, indicating excellent pulse signal quality. This demonstration of Ta2AlC MAX phase film Q-switched laser may open promising possibilities for scientific applications such as material processing.

Ultrafast dissipative soliton generation in anomalous dispersion achieving high peak power beyond the limitation of cubic nonlinearity

The maximum peak power of ultrafast mode-locked lasers has been limited by cubic nonlinearity, which collapses the mode-locked pulses and consequently leads to noisy operation or satellite pulses. In this paper, we propose a concept to achieve mode-locked pulses with high peak power beyond the limitation of cubic nonlinearity with the help of dissipative resonance between quintic nonlinear phase shifts and anomalous group velocity dispersion. We first conducted a numerical study to investigate the existence of high peak power ultrafast dissipative solitons in a fiber cavity with anomalous group velocity dispersion (U-DSAD) and found four unique characteristics. We then built long cavity ultrafast thulium-doped fiber lasers and verified that the properties of the generated mode-locked pulses match well with the U-DSAD characteristics found in the numerical study. The best-performing laser generated a peak power of 330 kW and a maximum pulse energy of 80 nJ with a pulse duration of 249 fs at a repetition rate of 428 kHz. Such a high peak power exceeds that of any previous mode-locked pulses generated from a single-mode fiber laser without post-treatment. We anticipate that the means to overcome cubic nonlinearity presented in this paper can give insight in various optical fields dealing with nonlinearity to find solutions beyond the inherent limitations.

An Optimized PV-Based Multi-Port Plug-In EV Charger Using Improved Particle Swarm Optimization Algorithm

In order to significantly improve the factor power and State of Charge, we proposed a design of Particle Swarm Optimization (PSO) with Maximum Power Point Tracking (MPPT) and control the Pulse Width Modulation (PWM) by PI controller that improves performance and reduces losses than other two existing works such as PV grid system designed with PI controller and P&O with MPPT and Fuzzy control-based PV grid system for EV charging. Here, the proposed PSO technique is improved by adding frequency scaling. The photovoltaic (PV) controlling, maximum power tracking and pulse generation are improving the result by adopting Improved Particle Swarm Optimization (IPSO). Multi-port charging station utilizes battery. After, getting the voltage link DC, the grid utilization is fed with the inverter logic. Here, the multi-port charger with PV and convertor boost DC-DC is directly interfaced with the electric vehicles (EV) charging port; additionally, the battery stores the energy. Depends on the utility grid, the energy is utilized. Thus, the proposed method attains the result of efficient multi-port utility, improved percentage of State of Charge (SoC), and better switching circuit with PFC and larger load utility. Overall, the proposed work is done in the 2018a version that adaptation with MATLAB/Simulink.

Enhanced Q-switched pulse generation at 1.5 µm in erbium-doped fiber laser using Thin-Film Dititanium Tin Carbide as a saturable absorber

In this study, we demonstrate the utilization of a saturable absorber (SA) based on the Thin-Film Dititanium Tin Carbide (Ti2SnC), a novel MAX phase material, in a Q-switched erbium-doped fiber laser (EDFL) operating at 1.5 µm. The Ti2SnC was effectively integrated with an EDFL cavity to modulate cavity loss and facilitate Q-switching. The resultant SA was produced through a synergistic combination of Ti2SnC and polyvinyl alcohol (PVA), forming a thin film. The Q-switched operation exhibited high stability, achieving an impressive signal-to-noise ratio (SNR) of 65.41 dB. The laser operated within a pump power range of 67.75 mW to 115.99 mW, correlating to a laser diode current of 130–220 mA. This resulted in output power ranging from 2.33 to 6.65 mW, exhibiting a slope efficiency of 1.57%. The Q-switched laser generated pulses at a wavelength of 1531.25 nm, with the repetition rate varying from 64.18 kHz to 105.9 kHz. This corresponded to a pulse width between 5.68 and 3.00 µs. The maximum pulse energy obtained in our study was 62.80 nJ. Additionally, the 3 dB spectral bandwidth was measured to be 1.3 nm. These experimental results highlight the potential of Ti2SnC, as a cost-effective, efficient, and practical option for saturable absorbers in Q-switched fiber lasers, thereby paving the way for further developments in photonic applications.

1178 nm self-Q-switched Raman laser generation enabled by BaTeW2O9 crystal

Multifunctional composite crystals have received great attention as an effective way to simplify the laser cavity. In this work, a self-Q-switched Raman laser operating at 1178 nm is demonstrated by using a multifunctional composite crystal BaTeW2O9 (BTW). An acousto-optic modulator (AOM) with a diffraction efficiency of 74% is designed and fabricated based on the Raman crystal BTW. A 1064 nm pulsed laser with a maximum single pulse energy of 260.6 μJ corresponding to a pulse width of 42 ns is obtained by inserting the BTW AOM into the laser cavity with Nd: YAG as the laser gain medium. Then an 1178 nm self-Q-switched Raman laser with the maximum single pulse energy of 22.8 μJ corresponding to a pulse width of 10 ns is successfully obtained. This work not only provides a competitive multifunctional composite device that can simplify the Raman laser cavity design but also has guiding significance for the design and development of multifunctional composite crystals.

Highly Efficient O-Band Rectangular Pulse Emission in a Figure-of-Nine Bismuth-Doped Fiber Laser

Highly efficient rectangular pulse emission is significant in high energy O-band applications due to the zero dispersion of standard telecom optical fiber in the second telecommunication window. The rectangular pulse emission offers the peak power clamping, which avoids wave-breaking and maintains the fundamental repetition frequency with arbitrarily widened temporal pulse width of ultrafast laser at high pump powers. The current technology in the O-band rectangular pulse emission achieves the maximum pulse energy of ∼30 nJ with an efficiency of ∼1.06%. Here, we fabricated a single-mode bismuth-doped phosphosilicate optical fiber by the modified chemical vapour deposition technique. The Bi-doped phosphosilicate optical fiber was characterized by a peak absorption of ∼0.6 dB/m at 1250 nm and a high gain coefficient of ∼0.22 dB/m at 1320 nm. These parameters contribute to the generation of rectangular pulse with a pump power threshold of ∼227.7 mW in a figure-of-nine laser cavity. The maximum pulse energy was achieved as ∼197.7 nJ, whereas the laser efficiency is ∼14.3%. We presented an O-band rectangular pulse emission with the highest pulse energy and efficiency as compared to previous studies, whilst its all-fiber laser setup is robust and feasible for high pulse energy applications.

Dual-Wavelength Q-switched Fiber Laser Generation by Incorporating 2D Materials in D-SMS Fiber Structure

We demonstrate a dual-wavelength Q-switched fiber laser generation by inserting a combination of SM-MM-SM fiber and a d-shape structure. This combination is known as D-SMS fiber. By side-polishing an SM fiber with 1-dB loss, the d-shape fiber structure is obtained. Then the d-shape SM fiber is spliced to 25 cm long MM and SM fiber to form a D-SMS fiber structure. After inserting D-SMS fiber, a stable dual-wavelength presence at 1562.8 nm and 1563.8 nm (1 nm wavelength spacing). The pulse train generates once we deposited a graphene oxide solution onto the surface of the d-shape structure. This Q-switching operation mode obtained from 45 mW to 111 mW pump power with a maximum pulse energy of 56 nJ. The repetition rate and pulse width have been recorded from 34 kHz to 55 kHz and from 10.22 µs to 6.47 µs, respectively.

High pulse energy actively Q-switched dual-wavelength pumped Er:ZBLAN fiber laser at 3.5 µm

In order to further improve the single pulse energy of actively Q-switched fiber laser in deep mid-infrared region, a universal and simple mechanical switch (MS) was used to achieve the high pulse energy 3.5 µm Er:ZBLAN fiber laser in dual-wavelength pumping (DWP) system. The maximum pulse energy was 9.4 µJ at the repetition rate of 8.4 kHz and the corresponding pulse width and peak power was 578 ns and 16.3 W, respectively. However, the further improvement of the pulse energy was limited by the formation of multiple pulses as the pump power increasing. According to the results of the experiment and numerical calculation, the multiple pulses were caused by relaxation oscillation and it was influenced by the pump power, the modulation rate and duty cycle of MS. Meanwhile, the Q-switched 2.8 µm laser was also found in the system, and it would also reduce the pulse energy of 3.5 µm laser. Therefore, the pulse energy could be improved in the further.

A good beam quality Ho:GdVO4 laser pumped by thulium‐doped fiber laser at 1940 nm

AbstractWe demonstrate a Ho:GdVO4 solid‐state laser pumped by a thulium (Tm)‐doped fiber laser at 1940nm. In continuous wave mode, a maximum output power of 6.1 W was obtained under the absorbed pump power of 31.9 W with the slope efficiency of 24.3% at the temperature of 18°C. The wavelength of output laser was 2048.53 nm with full width at half maximum of 0.2 nm. In Q‐switched mode, a maximum single pulse energy of 0.94 mJ was obtained with a minimum pulse duration of 7.3 ns at the pulse repetition frequency of 5 kHz, corresponding to a peak power of 129 kW and an average output power of 4.7 W. The beam quality factor of M2 was 1.01 under the maximum absorbed pump power. To the best of our knowledge, 0.94 mJ is the highest single pulse energy in single holmium (Ho) doped GdVO4 laser pumped by Tm‐doped fiber laser at 1940 nm, and 1.01 is the best beam quality factor of M2 in Ho:GdVO4 laser pumped by a Tm‐doped fiber laser.